The present invention relates to tires. More particularly, it relates to the carcass reinforcement of tires.
Tires are reinforced by cords (metallic, rayon, aramid, polyester, nylon, etc.) arranged in plies, namely carcass plies which extend from one bead wire to the other, being practically always of radial type at the present time, and crown plies constituting, together with the carcass ply, the crown reinforcement known as the belt, plus at times other plies which play a reinforcing or protective role. On an industrial scale, these plies are prepared in the form of semi-finished products characterized, from a geometrical standpoint, by their width and by the angle which the cords form with respect to the longitudinal direction, and they are made up in the form of coils. These coils are then mounted on assembly machines for the manufacture of the tire.
In order to assure an excellent mechanical attachment of the tire to the wheel, the carcass ply is firmly anchored in the bead of the tire. In order to assure this anchoring, various architectures are possible; for example, the cords can be passed below a bead wire, around which they are turned up. The plan and the manufacturing data giving the different components of the tire, their nature and their precise location within the vulcanized tire are referred to as the "architecture".
Certain reinforcement architectures are also known in which a reinforcement is made directly from a single coil of cord, at the time of the building of the tire. Thus, for instance, it has become very common to hoop the crowns of high-speed tires by cord arranged at zero degree. Such a reinforcement is effected by winding the cord over the crown of the tire. Another example is provided by EP 0 582 196 in which it is proposed that the carcass reinforcement be formed from a cord which extends back and forth from one bead of the tire to the other, with the addition of circumferentially wound cords to serve the function of the bead wire.
Finally, in order to achieve the desired performance, different rubber mixes must be formulated, depending on whether they are used in the beads, in the side walls, in the shoulders or in the crown, and depending on the precise place in these different parts. In fact, the performances of tires depend both on the rubber compositions used and on the cords of the reinforcements, as well as on the arrangement of the latter and their material.
The tires formed in this manner give excellent results as to their performance on vehicles. However, their manufacture is still rather difficult and frequently costly.